1. Field of the Invention
This invention pertains generally to water amendment technology as it relates to altering the characteristics of a fluid stream to maintain a consistent mixture in the stream. In particular, the present invention is a substantial improvement to the process of amending irrigation water to ultimately improve soil and growing conditions in agricultural/turf applications by providing an engineered delivery system that incorporates an integral and unique dry bulk feed system, an automated variable-rate discharge capability, and an apparatus which may be easily integrated into an environment that requires more sophisticated controls than present art by incorporating a high level of automation.
For more than two decades, amendments have been applied directly to soil by hand, or by mechanical spreaders, as a means of improving soil structure and plant health. In more recent times, surface spreading has become less desirable in many applications due to dust concerns, semi-permanent irrigation lines, the presence of crops, soil compaction, labor cost, public perception and other such issues. Independent laboratory and university studies have indicated that soil will always take on the characteristics of the water it is irrigated with. Therefore, where feasible and desirable, an alternative to surface application is to amend the irrigation water itself. Better irrigation water results in better soil structure, and ultimately improves overall growing conditions similar to, and in some ways better than, traditional surface applications.
A particular focus of the present invention is in the turf area of agricultural industry. Golf courses, for example, are large users of irrigation water. With fresh water becoming increasingly more scarce, conservation measures are reaching the point of forcing golf courses, sports fields, parks and other “green” industry users to irrigate with effluent water. Wastewater treatment plants are highly regulated by governmental agencies that require and provide the guidance for treating all wastewater to the point that it meets minimum public safety and health standards. However, there is no legislation that requires effluent water to meet any further quality guidelines when the discharge is used for irrigation (as opposed to being simply discharged back into a river, lake or ocean).
The problem created is that the chemical makeup of straight effluent water often makes for poor irrigation water. Poor water creates poor soil conditions, and users then suffer from unhealthy turf and inefficient water use. Adding gypsum and/or other amendments to the effluent discharge can notably improve its irrigation qualities, making treated wastewater much more viable for use on golf courses and other turflagricultural environments. Over the last decade, many golf courses, in particular, have attempted to implement a process of dry amendment injection on site. However, the sheer size and capital cost of the specialized equipment necessary to inject dry amendments, such as gypsum, together with the logistics of storage, delivery and handling, have dramatically limited successful implementation on golf course property.
Therefore, it would be particularly advantageous and efficient to inject the amendments directly at the wastewater treatment plant serving the courses, parks, etc. In this manner, a single equipment installation can treat the effluent and improve its irrigation qualities for all of the users downstream. In this fashion, the injection equipment can be installed at a location where other industrial equipment already exists and would therefore be much more appropriate, and it would also eliminate the need for each and every irrigation site being served to own, operate and maintain its own injection equipment. Such a modem industrial application typically requires a high degree of automation and accurate and reliable operation under variable weather and water flow conditions. It is an object of the present invention to fill this need in a way, and to a level that has previously not been attained. Although effluent discharge water is of particular focus, fresh water, (including well, river, runoff, etc.), will often have poor irrigation characteristics as well, and the present invention is equally suited to treating any and all sources of irrigation water without limitation.
2. Description of the Prior Art
In recent years, several inventions have been designed to introduce gypsum and other dry amendments directly into irrigation water. U.S. Pat. Nos. 4,820,053 and 5,417,491 represent the most common systems in use in the agricultural/turf industry. U.S. Pat. Nos. 5,628,563, 5,765,945 and 5,681,109 represent similar devices in function. The object of all such current inventions focus on differing methods of mechanically or hydraulically blending dry amendments (e.g., gypsum), with a liquid (typically water), in an integral mixing vat or container, and then introducing the resulting slurry into irrigation water in some sort of controlled fashion.
In each case, the injection machine acts as the metering device, with the effective treatment rate determined and preset manually for each particular installation. Common methods of metering with present art are through the use of an orifice disc, mechanical screen(s), adjusting the slurry output flow rate, pre-loading a certain quantity of amendment, blending the slurry output with makeup water or other such means of restricting and/or controlling the amount of slurry as it is discharged from an integral mixing tank or container into the irrigation flow. Precision of the application rate using any of these, or other similar methods, is marginal at best.
Regardless of how it is metered, the appropriate amount of gypsum or any amendment to be injected in any given scenario is a function of the irrigation water flow rate in gallons per minute (“GPM”), in relation to the desired treatment level (typically expressed in milliequivalents per liter (“Meq/L”) or parts per million, (“PPM”)). In a typical agricultural environment, irrigation pumps are either on or off, meaning the flow rate is a known constant whenever the pump is operating, thus allowing present art to operate in an acceptable fashion given its limitations. In many installations, however, golf courses and wastewater treatment plants for example, the irrigation water flow can vary greatly and change rapidly. This means that a mechanically fixed rate of injection would either under-apply, or worse, over-treat the irrigation water.
For example, if gypsum is injected at rate in excess of what the water can scientifically absorb, it will not dissolve into solution and will instead precipitate out causing accelerated equipment wear and tear, and will begin clogging emitters, sprinklers and possibly the irrigation delivery system itself. Even with a fairly constant flow rate, natural water chemistry can still vary enough that frequent modification of the injection rate may be desirable to more precisely maintain a desired treatment level. Attempts to operate existing systems in applications of frequent and/or rapid changes in irrigation water flow rate or chemistry have been impractical or failed altogether, and is thus a particular focus and advantage of the present invention.
The holding capacity for the dry process material in existing systems is also necessarily limited to the capacity of the mixing tank or container (three tons or less is common). This requires refilling of the mixing tank/container manually by workmen who must dump in large quantities of bagged product, or by some other means of frequently refilling the injection machine. This can be expensive, labor intensive, inefficient and very undesirable in many applications. For example, at a golf course where irrigation occurs throughout the evening hours when no workman would typically be on duty. Further, as the machines are refilled or “charged,” the actual treatment rate is subject to great variation including complete stoppage. The present invention provides the means for true, continuous operation without interruption.
In some applications, a bulk storage silo has been situated near an injection machine to reduce the manual labor by using a common convey auger to dispense amendments from the storage silo directly into the mixing tank. These installations, however, have many limitations and fail to achieve the advantages of the present invention. As an adjunct, the storage silos are not engineered as an integral part of the injection process, and are therefore prone to process failures. Bridging, inconsistent or unreliable delivery, excessive dust emissions and high maintenance are common examples of defects.
For example, the most common form of bulk storage silos, including those currently used in conjunction with injection machines in the agricultural/turf industry, are of the standard “funnel flow” type. That is to say that the stored product will flow downward from the middle of the silo, leaving the outer product in place until the middle falls so far down that the outer material falls into the center void, creating the funnel effect. (Imagine how sand flows in an hourglass.) While dry bulk materials tend to flow freely when perfectly dry, they can become “sticky” when moisture is present. This causes amendments such as gypsum to J “bridge” in a generic, funnel flow silo, even with only a trace of excess free moisture. (Bridging means that a hollow void or cave is created near the bottom of the hopper, preventing any material from discharging.) This bridging phenomenon is further aggravated and magnified when a standard convey auger has been employed and has been slowed down in an attempt to provide for a metering function.
Excess free moisture will also cause certain dry amendments to adhere to the sidewalls of a storage silo, where it can then build up to several inches thick, eventually falling off in large chunks, restricting or even completely stopping product flow by clogging the small discharge opening at the bottom of the silo hopper. Any material adhesion increases the propensity of bridging and prevents uniform process flow as well. Such undesirable flow problems are common and unavoidable with existing systems, especially when operating in areas of high rainfall and/or high humidity (e.g. coastal regions). Due to its ultra fine grind and hygroscopic nature, ambient moisture is especially problematic when handling solution grade gypsum, which is the most common dry amendment injected in irrigation water applications.
Even without moisture, existing systems which employ a generic silo and standard convey auger to attempt a metering function are defective in other ways. For example, the flow characteristics of a standard bulk storage silo inherently dispenses product with varying bulk density. In addition, dry bulk materials are in and of themselves prone to widely varying bulk density, based on such elements as ambient air temperature, humidity, aeration, crystalline structure, particle size distribution and purity. A fixed or constant auger speed, as is the common practice in all known agricultural applications, does not compensate for changes in bulk density and the discharge volume is then subject to great variation, failing to achieve a uniform and accurate application rate. The present invention addresses all of these limitations by incorporating an integral storage silo featuring a product-specific “mass flow” design hopper, an automated variable-rate precision feed mechanism, and air-drying capability to control humidity inside the silo.
Another common defect with existing art is the lack of modem and remote automation of the entire process. Existing systems were clearly designed for primary use in a farm environment where extensive automation would be cost prohibitive and/or unnecessary. The present invention addresses the needs of more demanding environments, such as a wastewater treatment plant or other industrial facility where automated operation, control and monitoring is essential to integration of the injection system with other equipment or processes on site.
Lastly, a preferred embodiment of the present invention incorporates all of the necessary apparatus to carry out the entire treatment process, including the advantage of using dry powder amendments purchased in bulk form, in a single, integrated, protected and distinctly compact arrangement that prevents malfunction due to outside forces such as weather, unauthorized tampering or petty vandalism.